import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

public class UdpSever {
    private DatagramSocket socket = null;

    public UdpSever(int port) throws SocketException {
        //在服务器端手动指定端口号
        socket = new DatagramSocket(port);
    }

    public void start() throws IOException {
        //启动服务器
        System.out.println("服务器启动.......");

        while(true){
            //1.读取请求并解析
            DatagramPacket requestPacket = new DatagramPacket(new byte[1024], 1024);
            //将receive的二进制数据存储到requestPacket中了
            socket.receive(requestPacket);
            //将二进制数据转成字符串显示
            String request = new String(requestPacket.getData(), 0, requestPacket.getLength());

            //2.根据请求计算响应
            String response = process(request);

            //3.将响应返回给客户端
            DatagramPacket responsePacket = new DatagramPacket(
                    response.getBytes(),
                    0,
                    response.getBytes().length,
                    requestPacket.getSocketAddress());
            socket.send(responsePacket);

            //4.打印日志
            System.out.printf("[%s, %d] req = %s, resp=%s ",
                    requestPacket.getAddress().toString(),
                    requestPacket.getPort(),
                    request,
                    response);
        }
    }
    public static String process(String request) {
        return request;
    }

    public static void main(String[] args) throws IOException {
        UdpSever sever = new UdpSever(9090);
        sever.start();
    }
}
